budget is budget, but the machine you're building there is horribly outdated. In cases like yours I actually do recommend going with a decent prefab because you're better off. Dell has a model for about $600 that I was really impressed with, it even has dedicated video... not that onboard stuff. I don't recall the model number, unfortunately but if you browse their website I'm sure you'll find it.
Even if you want to put together your own rig, with some digging I am sure you can build up something better than that for around the same price. Try using pricegrabber.com to find the lowest prices on your components.
You will need AT LEAST:
-A motherboard that supports dual-core processors, has at least 1 pci-e 16x slot and supports DDR2 memory up to 800 mhz. go with integrated audio.
-A dual-core processor
-A dedicated pci video card with 256 mb or more VRAM
1 GB of DDR2 RAM.
Cooler Master HAF 922 case
Thermaltake 750 watt modular psu
MSI P67A-C43 board
8 GB Corsair XMS DDR3 1300
Intel core i5 Sandy Bridge quad core@ 3.3 ghz
MSI GTX 570
WD 2 TB HDD
64-bit Windows 7
Rosewill USB Wirless Adapter
LG Blu-Ray DVD Combo Drive
I'm a PC!